JP3359493B2 - Semiconductor pressure transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure transducer for detecting a differential pressure or pressure, and more particularly, to a polygonal semiconductor chip having a polygonal diaphragm formed so that its diagonal line is orthogonal to the diagonal line of the semiconductor chip. The present invention relates to a semiconductor pressure transducer.

[0002]

2. Description of the Related Art Heretofore, as a semiconductor pressure transducer for detecting a differential pressure or pressure, a semiconductor pressure transducer utilizing a Si (silicon) semiconductor diaphragm is known. In this Si diaphragm type semiconductor pressure transducer, a gauge (diffusion resistance) acting as a piezoresistive region is formed on the surface of a substrate made of a semiconductor crystal by an impurity diffusion or ion implantation technique, and a lead is formed by vapor deposition of Al or the like. And
A thin portion having a thickness of about 20 μm to 60 μm, that is, a diaphragm is formed by removing a part of the back surface by etching. When measuring the differential pressure and the liquid level, the high pressure side and the low pressure side pressure are respectively applied to the front and back surfaces of the diaphragm, and the stress generated in the diaphragm changes according to the pressure difference. The value changes due to the stress generated in the diaphragm, the output voltage accompanying the resistance change at this time is detected, and the differential pressure or pressure is measured.

As a semiconductor chip, a circular chip having a circular diaphragm has been generally used.
Recently, a plurality of square chips having a circular diaphragm can be easily obtained by cutting a crystal wafer.
No. 4874) and a square chip having a square diaphragm are becoming common. In particular, when the shape of the diaphragm is a square, anisotropic etching that can be easily controlled in size and reduced in size can be performed because side etching does not occur when etching a square recess on the back side of the chip. Can be.

FIGS. 10 and 11 are a plan view and a sectional view showing a conventional example of a semiconductor pressure transducer. In the semiconductor pressure transducer 1, a square diaphragm 3 is formed at the center of a square semiconductor chip 2 such that diagonals a, a thereof are orthogonal to diagonals b, b of the semiconductor chip.
On the pedestal 4. For this reason, the diaphragm 3 is formed at an angle of 45 ° with respect to the semiconductor chip 2. The semiconductor chip 2 is made of p-type single-crystal Si having a (100) crystal plane orientation, the concave portion 5 is formed on the back surface side by the formation of the diaphragm 3 by etching, and the outer peripheral portion forms the thick portion 2a. 4.

In the vicinity of the edge of the surface of the diaphragm 3, four diffusion resistors 6a to 6d which function as piezo regions and detect a differential pressure or pressure are provided with diagonal lines b and b of the semiconductor chip 2.
b. The four diffused resistors 6a to 6d correspond to the crystal plane orientation (100) of the semiconductor chip 2.
Is formed in parallel with the <110> crystal axis direction in which the piezoresistance coefficient is maximized. Such a diffusion resistor 6a-
6d is formed by a diffusion or ion implantation method, and is connected to a wheel stone bridge to differentially output differential pressure signals of the low pressure and the high pressure P1, P2 applied to the front and back surfaces of the diaphragm 3. The resistance change rate at this time is represented by the following equation. _{ΔR / R = π 44 (σr} -σθ) / 2 ····· (1) However, [pi ₄₄ piezo resistance coefficient, .sigma.r perpendicular stress to the side of the diaphragm, Shigumashita the stress parallel to the sides of the diaphragm is there.

The pedestal 4 is made of Pyrex glass, ceramics or the like whose coefficient of thermal expansion is close to that of the semiconductor chip 2, and has a central portion through a recess 5 formed on the rear surface side of the semiconductor chip 2. A through-hole 7 is formed on the side for guiding the pressure P1 on the low pressure side to be measured.

[0007]

In the conventional semiconductor pressure transducer 1 described above, the material of the semiconductor chip 2 is silicon, and the pedestal 4 is made of Pyrex glass, ceramics or the like in consideration of the influence of thermal expansion. However,
Even when the difference between the pressures P1 and P2 applied to both surfaces of the diaphragm 3 is zero, if the temperature or the static pressure changes, σr-σθ in the above equation (1) does not become zero due to the difference and shape of the material, and an output is generated. Therefore, there is a problem that the zero point shifts. In particular, the shape of the semiconductor chip 2 is not problematic in the case of a circular chip having a circular diaphragm because it has symmetry with respect to the axis of the semiconductor chip. Due to the static pressure, σr ≠ σθ, and the resistance value changes. Therefore, a zero shift occurs, the differential pressure cannot be detected with high accuracy, and it is necessary to take measures for electronically compensating the signal.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. It is an object of the present invention to minimize a zero shift due to temperature and static pressure and its variation, and to provide a semiconductor pressure converter having good temperature characteristics. To provide equipment.

[0009]

According to the present invention, a polygonal diaphragm is formed at the center of a polygonal semiconductor chip at an angle of about 45 ° with respect to the semiconductor chip, and the edge of the diaphragm is formed at the center of the polygonal semiconductor chip. In a semiconductor pressure transducer in which a diffusion resistor is provided on a diagonal line of the semiconductor chip in the vicinity and a thick portion of the semiconductor chip is joined to a pedestal, a stress generated in the diffusion resistance in a diagonal direction of the semiconductor chip and perpendicular to the diagonal line. A non-joining portion is provided between the corner of the semiconductor chip and the pedestal so that the stresses in the directions are equal. Further, the present invention is characterized in that at least one of the semiconductor chip and the pedestal is provided with a step portion for forming a non-joining portion.

A polygonal semiconductor chip having a polygonal diaphragm does not exhibit axial symmetry with respect to the axis of the semiconductor chip. Therefore, when the pedestal is joined to the entire back surface of the semiconductor chip, the stress at the position where the diffusion resistance is formed is reduced. Is that the stress σr toward the center of the diaphragm is larger than the stress σθ in the direction perpendicular to the direction, and σr> σθ.
When the joint between the pedestal and the semiconductor chip is reduced, the stress σ in the direction perpendicular to the center of the diaphragm
θ increases, and σr <σθ. Therefore, when a non-bonded portion is provided between the semiconductor chip and the pedestal and the ratio of the length of the non-bonded portion to the length of the bonded portion is optimized, σr = σθ,
The rate of change of the resistance value is theoretically zero.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a plan view showing an embodiment of a semiconductor pressure transducer according to the present invention, and FIG. 2 is a sectional view taken along line II-II of FIG. The same components as those shown in the section of the prior art are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. In these figures,
The square semiconductor chip 2 has a square diaphragm 3 formed at an inclination of about 45 °, and the thick part 2 a is anodically bonded on the pedestal 4. In this case, the entire back surface of the thick portion 2a is not joined to the pedestal 4, but each corner is
The non-joined portion 13 is formed by being separated from the pedestal 4 by forming 0. The size of the step portion 10, in other words, the size of the non-bonded portion 13, depends on the stress σr generated in the diffusion resistors 6 a to 6 d in the diagonal direction of the semiconductor chip (the direction perpendicular to the side of the diaphragm) and the direction perpendicular to the diagonal line (the (In the direction parallel to the side). In other words, σr = σθ by optimizing the ratio A / B between the length A of the non-joined portion 13 and the length B of the joined portion 13A. Other configurations are the same as those of the above-described conventional semiconductor pressure transducer.

The bonding surface between the semiconductor chip 2 and the pedestal 4 is related to the deformation of the diaphragm 3. When the square diaphragm 3 is formed at an angle of 45.degree. 2 is longer in the diagonal direction, so that when the entire back surface of the thick portion 2a is joined, the stress σr perpendicular to the side of the diaphragm 3 becomes the stress σθ parallel to the side of the diaphragm 3.
Be larger.

Therefore, when the non-joining portion 13 is provided by forming the step portion 10 and the length of the diagonal joining surface of the semiconductor chip 2 is reduced, the stress σr perpendicular to the side of the diaphragm 3 gradually decreases. And the stress σθ parallel to the side of the diaphragm 3 increases. Therefore, when the step portion 10 is formed to have an optimum size, the stress σr perpendicular to the side of the diaphragm 3 and the stress σθ parallel to the side of the diaphragm 3 can be made equal. As a result, the resistance change rate becomes zero, and the zero shift of the output due to temperature, static pressure, and the like can be reduced.

FIG. 3 is a plan view showing another embodiment of the present invention, and FIG. 4 is a sectional view taken along the line IV-IV of FIG. In this embodiment, an annular step portion 14 is formed on the outer peripheral portion of the upper surface of the pedestal 4 formed of a cylindrical body, and the non-joined portion 13 is formed by separating the back surface corner of the semiconductor chip 2 from the pedestal 4. Also in such a structure, since the non-joined portion 13 is provided, σr-σθ can be made zero, and the zero shift can be eliminated.

FIG. 5 is a plan view showing still another embodiment of the present invention, and FIG. 6 is a sectional view taken along line VI-VI of FIG. In this embodiment, one diffusion resistor 6 is formed in the diaphragm 3, and the back surface corner on the diffusion resistor 6 side is formed as a non-joined portion 13 by forming a step portion 10. The diffused resistor 6 is connected to an external resistor to form a wheelstone bridge circuit. Also in such a structure, σr−σθ can be made zero as in the above-described embodiment, and the zero shift can be eliminated.

FIG. 7 is a plan view showing still another embodiment of the present invention, and FIG. 8 is a sectional view taken along line VIII-VIII of FIG. In this embodiment, two diffused resistors 6a and 6c are formed in the vicinity of two adjacent sides of the diaphragm 3, and the corners on the back surface of these diffused resistors 6a and 6c are not formed by the step 10. The joint 13 is provided. The two diffusion resistors 6a and 6c form a half-wheelstone bridge circuit whose circuit configuration is easy. Also in such a structure, since the back surfaces of the two corners facing the diffusion resistors 6a and 6c are formed as the non-joined portions 13 by forming the step portions 10, the same effects as in the above-described embodiment can be obtained.

[0017]

FIG. 9 shows the results of an experiment conducted to confirm the effects of the present invention. The semiconductor pressure transducer used in the experiment was obtained by joining a square pillar made of Pyrelex glass to a silicon square semiconductor chip by anodic bonding, and three dimensions were confirmed. The vertical axis in FIG. 9 is the stress (σr−σθ), and the horizontal axis is the ratio (A / B) of the length of the non-joined portion A and the joined portion B (see FIG. 1) on the diagonal line. Also crosses σr−σθ = 0, and A,
It is clear that the value of B can eliminate the zero shift.

It should be noted that the present invention is not limited to the above-described embodiment, and the shape of each part of the semiconductor pressure transducer,
The structure and the like can be appropriately modified and changed. For example, the pedestal 4 is formed in a cylindrical body, but may be formed in the same prism as the square semiconductor chip 2. In that case, the non-joined portion 13
May be formed only on the upper surface of the pedestal 4 or may be formed over the entire length of the corner in the height direction to form an octagon. Also, the square semiconductor chip 2 may be composed of two silicon plates, and the effect is exhibited when applied to the junction of the silicon plates. Further, in each of the above-described embodiments and examples, an example is shown in which a square diaphragm is formed on a square semiconductor chip. However, the present invention is not limited to this, and the octagonal semiconductor chip has a square diaphragm. May be formed, or an octagonal diaphragm may be formed on a square semiconductor chip.

[0019]

As described above, in the semiconductor pressure transducer according to the present invention, a polygonal diaphragm is formed at the center of a polygonal semiconductor chip at an angle of about 45 ° with respect to the semiconductor chip, and the edge of the diaphragm is formed. In a semiconductor pressure transducer in which a diffusion resistor is provided on a diagonal line of the semiconductor chip in the vicinity and a thick portion of the semiconductor chip is joined to a pedestal, a stress generated in the diffusion resistance in a diagonal direction of the semiconductor chip and perpendicular to the diagonal line. Since the non-joined portion is provided between the corner of the semiconductor chip and the pedestal so that the stresses in the directions are equal, a zero shift due to temperature or static pressure does not occur, and a semiconductor pressure transducer having a good temperature characteristic can be obtained. Can be provided. In addition, since the diaphragm is formed in a square shape, dimensional control when forming the step portion is easy, and anisotropic etching can be performed, so that downsizing can be achieved.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a semiconductor pressure transducer according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a plan view showing another embodiment of the present invention.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a plan view showing still another embodiment of the present invention.

FIG. 6 is a sectional view taken along line VI-VI of FIG. 5;

FIG. 7 is a plan view showing still another embodiment of the present invention.

8 is a sectional view taken along line VIII-VIII in FIG.

FIG. 9 is a graph showing a relationship between a ratio of a non-joined portion and a joined portion and a difference between a stress perpendicular to the side and a stress parallel to the side.

FIG. 10 is a plan view showing a conventional example of a semiconductor pressure transducer.

FIG. 11 is a sectional view of the converter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor pressure transducer, 2 ... Semiconductor chip, 3 ... Diaphragm, 4 ... Base, 5 ... Depressed part, 6, 6a-6d ... Diffusion resistance, 10 ... Stepped part, 13 ... Non-joined part, 14 ... Stepped part .

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01L 9/00-9/04 G01L 19/00-19/04 H01L 29/84

Claims (2)

(57) [Claims] 1. A polygonal diaphragm is formed at the center of a polygonal semiconductor chip at an angle of approximately 45 ° with respect to the semiconductor chip, and a diffusion resistor is provided on a diagonal line of the semiconductor chip near an edge of the diaphragm. In a semiconductor pressure transducer in which a thick portion of a semiconductor chip is joined to a pedestal, a corner of the semiconductor chip is formed so that a stress in a diagonal direction of the semiconductor chip generated in the diffusion resistance is equal to a stress in a direction perpendicular to the diagonal line. A non-joining part is provided between the semiconductor pressure transducer and the pedestal. 2. The semiconductor pressure transducer according to claim 1, wherein a step portion forming a non-joining portion is provided on at least one of the semiconductor chip and the pedestal.